[Regression Potential]
The fix is limited to the MAAS provider in the codebase; so regression potential is limited in scope of provider.

[Original Bug Report]
In a saucy MAAS environment, I had machines allocated to the admin user that were deployed using maas-cli (not using juju). These were perfectly running machines. However, while trying to use juju I noticed that a 'juju destroy-environment' put the machines that were 'allocated to admin' back to a 'Ready' state. These machines were not being used / controller by juju, but rather by maas-cli.

This means that juju destroys all of the machines regardless of whether they are being used by juju or not.

Looks like we never added anything to tag the machines with their environment.

Implementation note: *please* tag with environment UUID, not environment name (names are not globally unique, and environments will be referencing one another one day: treating the name as anything other than an alias is counterproductive).

One solution to fix this problem would be this:
- when the env is bootstrapped: create a tag named after the environment UUID
- each time juju takes control of a node: associate that tag with the node
- when juju fetches the list of instances it controls, only return the nodes associated with that tag

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

The verification of this Stable Release Update has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regresssions.